Lubricating oil composition

ABSTRACT

The present invention provides a lubricating oil composition comprising a base oil, an aspartic acid derivative and an aliphatic amine compound. The lubricating oil composition is ideal as an industrial lubricating oil such as for example for a hydraulic working oil in hydraulic equipment. 
     Primary amine, secondary amine, diamine, and/or tertiary amines may be employed for the aliphatic amine compound.

The present invention relates to lubricating oil compositions, in particular to be used as industrial lubricating oils, in particular to lubricating oil compositions used as for example machine oil, hydraulic fluid, turbine oil, compressor oil, gear oil, sliding surface oil, bearing oil or calibration oil.

Lubricating oil employed for mechanical equipment is required to be essentially rustproof in order to maintain its performance. Reasons for this include: raising and lowering of the lubricating oil temperature in the tank in the mechanical equipment, depending on conditions of use, which may cause admixture of condensed water with the lubricating oil in the tank; and admixture of moisture that may occur due to leakage of water from the cooling water piping. Aspartic acid esters etc are employed in order to obtain such rustproofing. See Laid-open Japanese Patent Application No. H. 6-200268.

Also, in recent years, industrial lubricating oil compositions are required to have excellent frictional properties. This is because a high degree of energy-saving can be achieved by effectively lowering the frictional losses in mechanical devices by providing a low coefficient of friction (μ), i.e. by giving the lubricating oil low-friction properties. Also, although hydraulic equipment is commonly used in constructional machinery etc., if the coefficient of friction of the lubricating oil used for the hydraulic fluid is high, a micro sticking-slipping effect is generated in the sliding region of the packing for reciprocatory movement of the hydraulic cylinder, causing phenomena such as cylinder chattering, vibration, squeaking, or generation of abnormal noise, and making it impossible to control the hydraulic equipment accurately. In order to ensure accurate and smooth movement of the hydraulic cylinder it is therefore necessary to lower the friction of the lubricating oil.

A problem that the invention intends to solve is to obtain an industrial lubricating oil having excellent anti-rust properties and low friction, thereby permitting a high degree of energy-saving. When a lubricating oil composition that solves this problem is employed as the hydraulic fluid in hydraulic equipment, it becomes possible to control the hydraulic equipment accurately without phenomena such as hydraulic cylinder chattering, vibration, squeaking, or generation of abnormal noise. The present invention seeks to obtain a lubricating oil composition whereby generation of rust is suppressed, and that has excellent energy-saving properties and operating efficiency.

According to the present invention, a lubricating oil composition that is ideal as an industrial lubricating oil such as for example hydraulic fluid can be obtained by adding as additives an aspartic acid derivative and aliphatic amine compound to highly refined base oil and/or synthetic base oil.

A primary amine, secondary amine, diamine, or tertiary amine etc. may be employed as the aliphatic amine compound referred to above.

With the present invention, an excellent lubricating oil composition whereby generation of rust is suppressed and that is of low coefficient of friction can be obtained. By lowering the coefficient of friction, the frictional losses that are generated in various types of industrial equipment can be effectively decreased, making it possible to achieve energy-saving. Also when used as hydraulic fluid, thanks to the lowering of the coefficient of friction, phenomena such as chattering of the hydraulic cylinder, vibration, squeaking, or generation of abnormal noise can be eliminated and the hydraulic equipment can be controlled accurately.

As the base oil of the present lubricating oil composition, mineral oil, called highly refined base oil, or synthetic oil may be employed: in particular, base oil in the base oil category of the API (American Petroleum Institute) belonging to Group I, Group II, Group III or Group IV etc. may be employed, either alone or as a mixture. The base oil that is here employed may be of elementary sulphur content no more than 700 ppm, preferably no more than 500 ppm. Its density may be 0.8 to 0.9. The aromatic fraction may be less than 5%, preferably less than 3%.

Group I base oil includes for example paraffin-type mineral oil obtained by suitable combination of refining means such as solvent refining, hydrofining, and dewaxing of the lubricating oil fraction obtained by normal pressure distillation of crude oil. The index of viscosity may be 80 to 120, preferably 95 to 110 (ASTM D2270). The kinetic viscosity at 40° C. is preferably 2 to 680 mm²/s, and even more preferably 8 to 220 mm²/s (ASTM D445). Also the total sulphur may be less than 700 ppm, preferably less than 500 ppm. The total nitrogen may be less than 50 ppm, preferably less than 25 ppm. In addition, the aniline point may be 80 to 150° C., preferably 90 to 122° C.

Group II base oil includes for example paraffin-type mineral oil obtained by suitable combination of refining means such as hydrocracking and dewaxing of the lubricating oil fraction obtained by normal pressure distillation of crude oil. Group II base oil refined by for example Gulf Oil's hydrofining method has total sulphur of less than 10 ppm and aromatic content less than 5% and is ideal in the present invention. There is no particular restriction regarding the viscosity of such base oil and the viscosity index may be 80 to 120, preferably 100 to 120. The kinetic viscosity at 40° C. is preferably 2 to 680 mm²/s and even more preferably 8 to 220 mm²/s. Also the total sulphur may be less than 300 ppm, preferably less than 200 ppm, and even more preferably less than 10 ppm. The total nitrogen may be less than 10 ppm, preferably less than 1 ppm. In addition, the aniline point may be 80 to 150° C., preferably 100 to 135° C.

As the Group III base oil and Group II base oil there may suitably be employed for example paraffin-type mineral oil manufactured by a high degree of hydrofining of the lubricating oil fraction obtained by normal pressure distillation of crude oil or base oil generated by a dewaxing process, involving refining by the ISODEWAX process, in which dewaxing is performed by converting wax to isoparaffins, or base oil refined by Mobil's wax isomerization process. Products capable of being denoted as “synthetic oils” according to the decisions of NAD (National Advertising Division), which is responsible for advertising descriptions in America, are also included.

There is no particular restriction regarding the viscosity of such base oils, but the viscosity index may be 95 to 145, preferably 100 to 140. The kinetic viscosity at 40° C. is preferably 2 to 680 mm²/s and even more preferably 8 to 220 mm²/s. Also the total sulphur may be 0 to 100 ppm, preferably less than 10 ppm. The total nitrogen may be less than 10 ppm, preferably less than 1 ppm. In addition, the aniline point may be 80 to 150° C., preferably 100 to 135° C.

GTL (Gas To Liquid) synthesised by the Fischer-Tropsch technique of converting natural gas to a liquid is ideal as the base oil according to the present invention, since it has extremely low sulphur content and aromatic content and its paraffin constituent ratio is extremely high, and since it is of excellent oxidation stability and shows very little evaporation loss, compared with mineral base oil refined from crude oil. Though there is no particular restriction regarding the viscous properties of the GTL base oil, usually the viscosity index will be 130 to 180, more preferably 140 to 175. The kinetic viscosity at 40° C. is preferably 2 to 680 mm²/s and even more preferably 5 to 120 mm²/s. Also the total sulphur is usually less than 10 ppm, and the total nitrogen less than 1 ppm. An example of such a GTL base oil product is SHELL XHVI (Registered Trademark).

Examples of synthetic oils that may be mentioned include: polyolefins, alkyl benzenes, alkyl naphthalenes, esters, polyoxyalkylene glycols, polyphenyl esters, dialkyl diphenyl ethers, fluorine-containing compounds (for example perfluoro polyethers, or polyolefin fluorides), or silicone oils.

The polyolefins referred to above include polymers of various types of olefins and hydrides of these. Although the olefins may be chosen at will, specific examples that may be given include ethylene, propylene, butene, or α-olefins of carbon number 5 or more. In the manufacture of the polyolefins, one of the above olefins may be employed alone, or two or more may be employed in combination. In particular, polyolefins called poly-α-olefins (PAO) are ideal: these constitute Group IV base oils.

Although there is no particular restriction regarding the viscosity of these synthetic base oils, their kinetic viscosity at 40° C. is preferably 2 to 680 mm²/s, and even more preferably 8 to 220 mm²/s.

Although there is no particular restriction regarding the content of the above base oil in the lubricating oil composition according to the present invention, the content may be 60 weight %, preferably at least 80 weight %, more preferably at least 90 weight % and yet more preferably at least 95 weight % with reference to the total amount of the lubricating oil composition.

The aspartic acid derivatives are indicated by the following general formula (1):—

In the above general formula 1, X₁ and X₂ are respectively hydrogen or alkyl groups, alkenyl groups or hydroxyalkyl groups of carbon number 3 to 6, that may be the same or different, and may preferably respectively be 2-methyl propyl groups or tertiary butyl groups. X₃ may be an alkyl group or alkenyl group, alkyl group having an ether bond, or a hydroxyalkyl group, of carbon number 1 to 30. For example, it may be an octadecyl group, alkoxy propyl group, 3-(C6 to C18) hydrocarboxy (C3 to C6) alkyl group, or, more preferably, a cyclohexyl oxypropyl group, 3-octyl oxypropyl group, 3-iso-octyl oxypropyl group, 3-decyl oxypropyl group, 3-isodecyl oxypropyl group, or 3-(C12 to C16) alkoxypropyl group. X₄ may be a saturated or unsaturated carboxylic acid group of carbon number 1 to 30, or an alkyl group, alkenyl group or hydroxyalkyl group of carbon number 1 to 30. Examples are a propionic acid group or propionylic acid group.

The aspartic acid derivative may be of acid value 10 to 200 mgKOH/g, preferably 50 to 150 mgKOH/g, as determined by JIS K2501. The aspartic acid derivative may be employed in the amount of about 0.01 to 5 weight %, preferably about 0.05 to 2 weight %, in the lubricating oil composition. A single aspartic acid derivative, or a mixture of derivatives of a number of types may be employed.

This lubricating oil composition may be blended with an aliphatic amine compound. Examples of such aliphatic amine compounds that may be mentioned include primary amines indicated by the general formula (2), secondary amines indicated by the general formula (3), diamines indicated by the general formula (4) and tertiary amines indicated by the general formula (5).

H₂N—X₅  (2)

In this general formula 2, X₅ is an alkyl group or alkenyl group of carbon number 1 to 30. Examples that may be mentioned include: laurylamine, coconut amine, n-tridecylamine, myristylamine, n-pentadecylamine, n-palmitylamine, n-heptadecylamine, n-stearylamine, isostearylamine, n-nonadecylamine, n-eicosylamine, n-heneicosylamine, n-docosylamine, n-tricosylamine, n-pentacosylamine, oleylamine, tallow amine, tallow amine hydride, and soybean amine. Preferably X₅ is of carbon number 8 to 24 and more preferably of carbon number 12 to 18. Also X₅ may be a straight chain aliphatic, a branched chain aliphatic or tertiary alkyl group.

X₆—NH—X₇  (3)

In the above general formula 3, X₆ and X₇ are an alkyl group or alkenyl group of carbon number 1 to 30. Examples that may be cited include: dilaurylamine, di-coconut amine, di-n-tridecylamine, di-myristylamine, di-n-pentadecylamine, di-n-palmitylamine, di-n-heptadecylamine, di-n-stearylamine, di-isostearylamine, di-n-nonadecylamine, di-n-eicosylamine, di-n-heneicosylamine, di-n-docosylamine, di-n-tricosylamine, di-n-pentacosylamine, di-oleylamine, di-tallow amine, di-tallow amine hydride, and di-soybean amine. Preferably X₆ and X₇ are of carbon number 8 to 24 and more preferably of carbon number 12 to 18. X₆ and X₇ may be the same or different.

X₈—NH—X₉—NH₂  (4)

In general formula 4, X₈ may be an alkyl group or alkenyl group of carbon number 1 to 30. Preferably X₈ is of carbon number 8 to 24 and more preferably of carbon number 12 to 18. X₉ is an alkylene group of carbon number 1 to 12. Preferably X₉ is of carbon number 1 to 8, and more preferably of carbon number 2 to 4.

Examples that may be cited include ethylene diamines such as: N-octyl-1,2-ethylene diamine, N-nonyl-1,2-ethylene diamine, N-decyl-1,2-ethylene diamine, N-undecyl-1,2-ethylene diamine, N-lauryl-1,2-ethylene diamine, N-tridecyl-1,2-ethylene diamine, N-myristyl-1,2-ethylene diamine, N-tetradecyl-1,2-ethylene diamine, N-pentadecyl-1,2-ethylene diamine, N-palmityl-1,2-ethylene diamine, N-heptadecyl-1,2-ethylene diamine, N-oleyl-1,2-ethylene diamine, N-stearyl 1,2-ethylene diamine, N-isostearyl 1,2-ethylene diamine, N-nonadecyl 1,2-ethylene diamine, N-eicosyl 1,2-ethylene diamine, N-coconut-1,2-ethylene diamine, N-tallow 1,2-ethylene diamine, N-tallow 1,2-ethylene diamine hydride, and N-soybean 1,2-ethylene diamine.

Also, examples that may be cited include propylene diamines such as: N-octyl-1,3-propylene diamine, N-nonyl-1,3-propylene diamine, N-decyl-1,3-propylene diamine, N-undecyl-1,3-propylene diamine, N-lauryl-1,3-propylene diamine, N-tridecyl-1,3-propylene diamine, N-myristyl-1,3-propylene diamine, N-tetradecyl-1,3-propylene diamine, N-pentadecyl-1,3-propylene diamine, N-palmityl-1,3-propylene diamine, N-heptadecyl-1,3-propylene diamine, N-oleyl-1,3-propylene diamine, N-stearyl 1,3-propylene diamine, N-isostearyl 1,3-propylene diamine, N-nonadecyl 1,3-propylene diamine, N-eicosyl 1,3-propylene diamine, N-coconut-1,3-propylene diamine, N-tallow 1,3-propylene diamine, N-tallow 1,3-propylene diamine hydride, and N-soybean 1,3-propylene diamine.

Also, examples that may be cited include butylene diamines such as: N-octyl-1,4-butylene diamine, N-nonyl-1,4-butylene diamine, N-decyl-1,4-butylene diamine, N-undecyl-1,4-butylene diamine, N-lauryl-1,4-butylene diamine, N-tridecyl-1,4-butylene diamine, N-myristyl-1,4-butylene diamine, N-tetradecyl-1,4-butylene diamine, N-pentadecyl-1,4-butylene diamine, N-palmityl-1,4-butylene diamine, N-heptadecyl-1,4-butylene diamine, N-oleyl-1,4-butylene diamine, N-stearyl 1,4-butylene diamine, N-isostearyl 1,4-butylene diamine, N-nonadecyl 1,4-butylene diamine, N-eicosyl 1,4-butylene diamine, N-coconut-1,4-butylene diamine, N-tallow 1,4-butylene diamine, N-tallow 1,4-butylene diamine hydride, and N-soybean 1,4-butylene diamine.

X₁₀—N—(X₁₁)₂  (5)

In general formula 5, X₁₀ may be an alkyl group or alkenyl group of carbon number 1 to 30. Preferably X₁₀ is of carbon number 1 to 20, but is more preferably of carbon number 1 to 8 or 12 to 18. X₁₁ is an alkyl group, alkenyl group, or hydroxyalkyl group of carbon number 1 to 20: preferably the carbon number of X₁₁ is 1 to 8 or 12 to 18.

Examples of the case where X₁₀ is a methyl group include dialkyl methylamines such as: dioctyl methylamine, dinonyl methylamine, didecyl methylamine, diundecyl methylamine, dilauryl methylamine, ditridecyl methylamine, dimyristyl methylamine, ditetradecyl methylamine, dipentadecyl methylamine, dipalmityl methylamine, diheptadecyl methylamine, dioleyl methylamine, distearyl methylamine, diisostearyl methylamine, dinonadecyl methylamine, dieicosyl methylamine, di-coconut-methylamine, di-tallow methylamine, di-tallow methylamine hydride, and di-soybean methylamine.

Also, examples of the case where X₁₁ is a methyl group include alkyl dimethylamines such as: octyl dimethylamine, nonyl dimethylamine, decyl dimethylamine, undecyl dimethylamine, lauryl dimethylamine, tridecyl dimethylamine, myristyl dimethylamine, tetradecyl dimethylamine, pentadecyl dimethylamine, palmityl dimethylamine, heptadecyl dimethylamine, oleyl dimethylamine, stearyl dimethylamine, isostearyl dimethylamine, nonadecyl dimethylamine, eicosyl dimethylamine, coconut-dimethylamine, tallow dimethylamine, tallow dimethylamine hydride, and soybean dimethylamine.

Also, examples of the case where X₁₁ is a hydroxyalkyl group include N-alkyl diethanolamines such as: N-octyl diethanolamine, N-nonyl diethanolamine, N-decyl diethanolamine, N-undecyl diethanolamine, N-lauryl diethanolamine, N-tridecyl diethanolamine, N-myristyl diethanolamine, N-tetradecyl diethanolamine, N-pentadecyl diethanolamine, N-palmityl diethanolamine, N-heptadecyl diethanolamine, N-oleyl diethanolamine, N-stearyl diethanolamine, N-isostearyl diethanolamine, N-nonadecyl diethanolamine, N-eicosyl diethanolamine, N-coconut diethanolamine, N-tallow diethanolamine, N-tallow diethanolamine hydride, and N-soybean diethanolamine; and N-alkyl dipropanolamines such as: N-octyl dipropanolamine, N-nonyl dipropanolamine, N-decyl dipropanolamine, N-undecyl dipropanolamine, N-lauryl dipropanolamine, N-tridecyl dipropanolamine, N-myristyl dipropanolamine, N-tetradecyl dipropanolamine, N-pentadecyl dipropanolamine, N-palmityl dipropanolamine, N-heptadecyl dipropanolamine, N-oleyl dipropanolamine, N-stearyl dipropanolamine, N-isostearyl dipropanolamine, N-nonadecyl dipropanolamine, N-eicosyl dipropanolamine, N-coconut dipropanolamine, N-tallow dipropanolamine, N-tallow dipropanolamine hydride, and N-soybean dipropanolamine.

The aliphatic amine referred to above may be of base value 10 to 800 mg KOH/g as determined by JIS K2501, but is preferably of base value of 100 to 500 mg KOH/g. At least one such aliphatic amine, selected from the above group, may be employed in an amount of about 0.05 to 5 weight %, preferably about 0.01 to 1 weight %, in the lubricating oil composition, either alone or in suitable combination.

In order to further improve performance, apart from the constituents mentioned above, various additives may be suitably employed as required. Examples of these additives that may be mentioned include antioxidants, metal deactivators, extreme pressure agents, oiliness improvers, anti-foaming agents, viscosity index improvers, pour-point depressants, detergent-dispersants, rust inhibitors, anti-rust agents, demulsifiers etc. or other known lubricating oil additives.

As the antioxidants that may be employed in the present invention, antioxidants that are employed in lubricating oils are practically preferable; examples that may be mentioned include: phenol-based antioxidants, aromatic amine-based antioxidants, sulphur-based antioxidants and phosphorus-based antioxidants. One or a combination of more than one of these antioxidants may be employed in the range of 0.01 to 5 weight % with respect to 100 weight % of base oil.

Examples of the aromatic amine-based antioxidants that may be given include: dialkyl diphenylamines such as p,p′-dioctyl diphenylamine (manufactured by Seiko Chemicals Inc: Non-flex OD-3), p,p′-di-α-methylbenzyl diphenylamine, or N-p-butylphenyl-N-p′-octylphenylamine; monoalkyl diphenylamines such as mono-t-butyl diphenylamine or mono-octyl diphenylamine; bis(dialkylphenyl)amines such as di(2,4-diethylphenyl)amine, or di(2-ethyl-4-nonylphenyl)amine; alkylphenyl-1-naphthylamines such as octylphenyl-1-naphthylamine or N-t-dodecylphenyl-1-naphthylamine; aryl-naphthylamines such as 1-naphthylamine, phenyl-1-naphthylamine, phenyl-2-naphthylamine, N-hexylphenyl-2-naphthylamine, or N-octylphenyl-2-naphthylamine; phenylene diamines such as N,N′-diisopropyl-p-phenylene diamine, or N,N′-diphenyl-p-phenylenediamine; or phenothiazines such as phenothiazine (manufactured by Hodogaya Chemicals Inc: Phenothiazine) or 3,7-dioctyl phenothiazine.

Examples of phenol-based antioxidants include 2-t-butylphenol, 2-t-butyl-4-methylphenol, 2-t-butyl-5-methylphenol, 2,4-di-t-butylphenol, 2,4-dimethyl-6-t-butylphenol, 2-t-butyl-4-methoxyphenol, 3-t-butyl-4-methoxyphenol, 2,5-di-t-butyl hydroquinone (manufactured by Kawaguchi Chemicals Inc: Antage DBH), 2,6-di-t-butylphenol, 2,6-di-t-butyl-4-alkylphenols, such as 2,6-di-t-butyl-4-methylphenol, or 2,6-di-t-butyl-4-ethylphenol; or 2,6-di-t-butyl-4-alkoxyphenols such as 2,6-di-t-butyl-4-methoxyphenol or 2,6-di-t-butyl-4-ethoxyphenol.

Further examples include alkyl-3-(3,5-di-t-butyl-4-hydroxyphenyl) propionates such as 3,5-di-t-butyl-4-hydroxybenzyl mercapto-octyl acetate, n-octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl) propionate (manufactured by Yoshitomi Seiyaku Inc: Yoshinox SS), n-dodecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl) propionate, 2′-ethylhexyl-3-(3,5-di-t-butyl-4-hydroxyphenyl) propionate, or benzene propanoate 3,5-bis(1,1-dimethyl-ethyl)-4-hydroxy-C7 to C9 side-chain alkyl ester (manufactured by Ciba Speciality Chemicals Inc: Irganox L135), or 2,2′-methylene bis(bis 4-alkyl-6-t-butylphenol) such as 2,6-di-t-butyl-α-dimethylamino-p-cresol, 2,2′-methylene bis(4-methyl-6-t-butylphenol) (manufactured by Kawaguchi Chemicals Inc: Antage W-400), or 2,2′-methylene bis(4-ethyl-6-t-butylphenol) (manufactured by Kawaguchi chemicals: Antage W-500).

Yet further examples include bisphenols such as 4,4′-butylidene bis(3-methyl-6-t-butylphenol) (manufactured by Kawaguchi Chemicals Inc: Antage W-300), 4,4′-methylene bis(2,6-di-t-butylphenol) (manufactured by Shell Japan Inc: Ionox 220 AH), 4,4′-bis(2,6-di-t-butylphenol), 2,2-(di-t-hydroxyphenyl) propane (manufactured by Shell Japan Inc: bisphenol A), 2,2-bis(3,5-di-t-butyl-4-hydroxyphenyl)propane, 4,4′-cyclohexylidene bis(2,6-t-butylphenol), hexamethylene glycol bis[3-(3,5-di-t-butyl-4-hydroxyphenyl) propionate] (manufactured by Ciba Speciality Chemicals Inc: Irganox L109), triethylene glycol bis[3-(3-t-butyl-4-hydroxy-5-methylphenyl)propionate] (manufactured by Yoshitomi Chemicals Inc: Tominox 917), 2,2′-thio-[diethyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate] (manufactured by Ciba Speciality Chemicals Inc: Irganox L 115), 3,9-bis{1,1-dimethyl-2-[3-(3-t-butyl-4-hydroxy-5-methylphenyl)propionyloxy]ethyl} 2,4,8,10-tetraoxaspiro[5,5]undecane (Sumitomo Chemicals: Sumilizer GA80), or 4,4′-thiobis(3-methyl-6-t-butylphenol) (manufactured by Kawaguchi Chemicals Inc: Antage RC), or 2,2′-thio bis(4,6-di-t-butyl-resorcin).

Further examples that may be given also include polyphenols, such as tetrakis[methylene-3-(3,5-di-t-butyl-4-hydroxyphenyl) propionate]methane (manufactured by Ciba Speciality Chemicals Inc: Irganox L 110), 1,1,3-tris(2-methyl-4-hydroxy-5-t-butylphenyl)butane (manufactured by Yoshitomi Chemicals Inc: Yoshinox 930), 1,3,5-trimethyl-2,4,6-tris(3,5-di-t-butyl-4-hydroxybenzyl)benzene (manufactured by Shell Japan Inc: Ionox 330), bis-[3,3′-bis-(4′-hydroxy-3′-t-butylphenyl)butyric acid]glycol ester, 2-(3′,5′-di-t-butyl-4-hydroxyphenyl)methyl-4-(2″,4″-di-t-butyl-3″-hydroxyphenyl)methyl-6-t-butylphenol, or 2,6-bis(2′-hydroxy-3′-t-butyl-5′-methyl-benzyl)-4-methylphenol, or phenol/aldehyde condensation products such as the condensation product of p-t-butylphenol and formaldehyde or the condensation product of p-t-butylphenone and acetaldehyde.

As the sulphur-based antioxidants, there may be mentioned by way of example dialkyl sulphides such as didodecyl sulphide or dioctadecyl sulphide, thiodipropionic acid esters such as didodecyl thiodipropionate, dioctadecyl thiodipropionate, dimyristyl thiodipropionate, or dodecyl octadecyl thiodipropionate, or 2-mercapto benzoimidazole.

As the phosphorus-based antioxidants, there may be mentioned by way of example triaryl phosphites such as triphenyl phosphite, or tricresyl phosphite, trialkyl phosphites such as trioctadecyl phosphite, or tridecyl phosphite, or tridodecyl trithiophosphite.

Metal deactivators that may be used together with the composition according to the present invention include benzotriazole, 4-alkyl-benzotriazoles such as 4-methyl-benzotriazole, or 4-ethyl-benzotriazole, 5-alkyl-benzotriazoles such as 5-methyl-benzotriazole, or 5-ethyl-benzotriazole, 1-alkyl-benzotriazoles such as 1-dioctyl-aminomethyl-2,3-benzotriazole, benzotriazole derivatives such as 1-alkyl-tolutriazoles such as 1-dioctyl aminomethyl-2,3-tolutriazole, benzoimidazole, 2-(alkyl dithio)-benzoimidazoles such as 2-(octyl dithio)-benzoimidazole, 2-(decyl dithio)-benzoimidazole, or 2-(dodecyl dithio)-benzoimidazole, or benzoimidazole derivatives such as 2-(alkyl dithio)-toluimidazoles such as a 2-(octyl dithio)-toluimidazole, 2-(decyl dithio)-toluimidazole, or 2-(dodecyl dithio)-toluimidazole.

Further examples include indazole or indazole derivatives such as toluindazoles such as 4-alkyl-indazoles or 5-alkyl-indazoles, benzothiazole, or benzothiazole derivatives such as 2-mercapto benzothiazole derivatives (Chiyoda Chemicals Inc: Thiolite B-3100), 2-(alkyl dithio) benzothiazoles such as 2-(hexyl dithio) benzothiazole, 2-(alkyl dithio) toluthiazoles such as 2-(octyl dithio) benzothiazole, 2-(hexyl dithio) toluthiazole, 2-(octyl dithio) toluthiazole, 2-(N,N-dialkyl dithiocarbamyl)benzothiazoles such as 2-(N,N-diethyl dithiocarbamyl)benzothiazole, 2-(N,N-dibutyl dithiocarbamyl)benzothiazole or 2-(N,N-dihexyl dithiocarbamyl)benzothiazole, or 2-(N,N-dialkyl dithiocarbamyl) toluthiazoles such as 2-(N,N-diethyl dithiocarbamyl) toluthiazole, 2-(N,N-dibutyl dithiocarbamyl) toluthiazole or 2-(N,N-dihexyl dithiocarbamyl) toluthiazole.

Yet further examples include benzo-oxazole derivatives such as 2-(alkyl dithio)-benzo-oxazoles such as 2-(octyl dithio) benzo-oxazole, 2-(decyl dithio) benzo-oxazole, or 2-(dodecyl dithio) benzo-oxazole, or 2-(alkyl dithio)-toluoxazoles such as 2-(octyl dithio) toluoxazole, 2-(decyl dithio) toluoxazole, or 2-(dodecyl dithio) toluoxazole, thiadiazole derivatives such as 2,5-bis(alkyl dithio)-1,3,4-thiadiazoles such as 2,5-bis(pentyl dithio)-1,3,4-thiadiazole, 2,5-bis(nonyl dithio)-1,3,4-thiadiazole, 2,5-bis(dodecyl dithio)-1,3,4-thiadiazole or 2,5-bis(octadecyl dithio)-1,3,4-thiadiazole, such as 2,5-bis(N,N-dialkyl dithiocarbamyl)-1,3,4-thiadiazoles such as 2,5-bis(N,N-diethyl dithiocarbamyl)-1,3,4-thiadiazole, 2,5-bis(N,N-dibutyl dithiocarbamyl)-1,3,4-thiadiazole, or 2,5-bis(N,N-dioctyl dithiocarbamyl)-1,3,4-thiadiazole, or 2-N,N-dialkyl dithiocarbamyl-5-mercapto-1,3,4-thiadiazoles such as 2-N,N-dibutyl dithiocarbamyl-5-mercapto-1,3,4-thiadiazole or 2-N,N-dioctyl dithiocarbamyl-5-mercapto-1,3,4-thiadiazole, or triazole derivatives such as 1-alkyl-2,4-triazoles such as 1-di-octyl aminomethyl-2,4-triazole.

One, or a combination of more than one, of these metal deactivators may be employed in a range of 0.01 to 0.5 weight % with respect to 100 weight % of base oil.

A phosphorus compound may be added to the lubricating oil composition according to the present invention and further improvement in wear-resistance and extreme pressure performance may thereby be conferred. Examples that may be mentioned of suitable phosphorus compounds according to the present invention include: phosphoric acid esters, acid phosphoric acid esters, amine salts of acid phosphoric acid esters, phosphorous acid esters, phosphorothionates, zinc dithiophosphates, phosphorus-containing carboxylic acids, and phosphorus-containing carboxylic acid esters. One, or a combination of more than one, of these phosphorus compounds may be employed in a range of 0.01 to 2 weight % with respect to 100 weight % of base oil.

Examples of the above phosphoric acid esters that may be given include: tributyl phosphate, tripentyl phosphate, trihexyl phosphate, triheptyl phosphate, trioctyl phosphate, trinonyl phosphate, tridecyl phosphate, triundecyl phosphate, tridodecyl phosphate, tritridecyl phosphate, tritetradecyl phosphate, tripentadecyl phosphate, trihexadecyl phosphate, triheptadecyl phosphate, trioctadecyl phosphate, trioleyl phosphate, or triphenyl phosphate, tris(isopropylphenyl) phosphate, triallyl phosphate, tricresyl phosphate, trixylenyl phosphate, cresyl diphenyl phosphate, or xylenyl diphenyl phosphate.

Specific examples of the above acid phosphoric acid esters that may be given include: monobutyl acid phosphate, monopentyl acid phosphate, monohexyl acid phosphate, monoheptyl acid phosphate, mono-octyl acid phosphate, monononyl acid phosphate, monodecyl acid phosphate, monoundecyl acid phosphate, monododecyl acid phosphate, monotridecyl acid phosphate, monotetradecyl acid phosphate, monopentadecyl acid phosphate, monohexadecyl acid phosphate, monoheptadecyl acid phosphate, mono-octadecyl acid phosphate, mono-oleyl acid phosphate, dibutyl acid phosphate, dipentyl acid phosphate, dihexyl acid phosphate, diheptyl acid phosphate, dioctyl acid phosphate, dinonyl acid phosphate, didecyl acid phosphate, diundecyl acid phosphate, didodecyl acid phosphate, ditridecyl acid phosphate, ditetradecyl acid phosphate, dipentadecyl acid phosphate, dihexadecyl acid phosphate, diheptadecyl acid phosphate, dioctadecyl acid phosphate or dioleyl acid phosphate.

As the amine salts of acid phosphoric acid esters, there may be mentioned for example salts of the acidic phosphoric acid esters with amines such as methylamine, ethylamine, propylamine, butylamine, pentylamine, hexylamine, heptylamine, octylamine, dimethylamine, diethylamine, dipropylamine, dibutylamine, dipentylamine, dihexylamine, diheptylamine, dioctylamine, trimethylamine, triethylamine, tripropylamine, tributylamine, tripentylamine, trihexylamine, triheptylamine and trioctylamine.

As the phosphorous acid esters there may be mentioned for example dibutyl phosphite, dipentyl phosphite, dihexyl phosphite, diheptyl phosphite, dioctyl phosphite, dinonyl phosphite, didecyl phosphite, diundecyl phosphite, didodecyl phosphite, dioleyl phosphite, diphenyl phosphite, dicresyl phosphite, tributyl phosphite, tripentyl phosphite, trihexyl phosphite, triheptyl phosphite, trioctyl phosphite, trinonyl phosphite, tridecyl phosphite, triundecyl phosphite, tridodecyl phosphite, trioleyl phosphite, triphenyl phosphite, or tricresyl phosphite.

Specific examples of the phosphorothionates that may be mentioned include tributyl phosphorothionate, tripentyl phosphorothionate, trihexyl phosphorothionate, triheptyl phosphorothionate, trioctyl phosphorothionate, trinonyl phosphorothionate, tridecyl phosphorothionate, triundecyl phosphorothionate, tridodecyl phosphorothionate, tritridecyl phosphorothionate, tritetradecyl phosphorothionate, tripentadecyl phosphorothionate, trihexadecyl phosphorothionate, triheptadecyl phosphorothionate, trioctadecyl phosphorothionate, trioleyl phosphorothionate, triphenyl phosphorothionate, tricresyl phosphorothionate, trixylenyl phosphorothionate, cresyl diphenyl phosphorothionate, xylenyl diphenyl phosphorothionate, tris(n-propylphenyl) phosphorothionate, tris(isopropylphenyl) phosphorothionate, tris(n-butylphenyl) phosphorothionate, tris(isobutylphenyl) phosphorothionate, tris(s-butylphenyl) phosphorothionate, or tris(t-butylphenyl) phosphorothionate. Mixtures of these may also be employed.

Specific examples of the zinc dithiophosphates that may be mentioned typically include zinc dialkyl dithiophosphates, zinc diaryl dithiophosphates, or zinc arylalkyl dithiophosphates. For example zinc dialkyl dithiophosphates may be employed wherein the alkyl group of the zinc dialkyl dithiophosphate is a primary or secondary alkyl group of carbon number 3 to 22, or having an alkylaryl group substituted by an alkyl group of carbon number 3 to 18. Specific examples of the zinc dialkyl dithiophosphates that may be mentioned include zinc dipropyl dithiophosphate, zinc dibutyl dithiophosphate, zinc dipentyl dithiophosphate, zinc dihexyl dithiophosphate, zinc diisopentyl dithiophosphate, zinc diethylhexyl dithiophosphate, zinc dioctyl dithiophosphate, zinc dinonyl dithiophosphate, zinc didecyl dithiophosphate, zinc didodecyl dithiophosphate, zinc dipropylphenyl dithiophosphate, zinc dipentylphenyl dithiophosphate, zinc dipropylmethylphenyl dithiophosphate, zinc dinonylphenyl dithiophosphate, zinc didodecylphenyl dithiophosphate, or zinc didodecylphenyl dithiophosphate.

As the phosphorus-containing carboxylic acids or phosphorus-containing carboxylic acid compounds such as esters thereof, so long as these contain both a carboxylic group and a phosphorus atom in the same molecule, there is no particular restriction as to their structure; however, from the point of view of extreme pressure performance and heat/oxidation stability, phosphorylated carboxylic acids or phosphorylated carboxylic acid esters are preferable.

As for phosphorylated carboxylic acids and phosphorylated carboxylic acid esters, compounds represented by for example the following formula (6) may be mentioned by way of example.

where, in the above formula 6, R4 and R5 may be the same or different and respectively indicate a hydrogen atom or hydrocarbon group of carbon number 1 to 30, R6 indicates an alkylene group of carbon number 1 to 20, R7 indicates a hydrogen atom or a hydrocarbon group of carbon number 1 to 30, X1, X2, X3 and X4 may be the same or different, and respectively indicate an oxygen atom or a sulphur atom.

As the hydrocarbon groups of carbon number 1 to 30 in R4 and R5 in the above general formula (6), examples that may be given include alkyl groups, alkenyl groups, aryl groups, alkylaryl groups or arylalkyl groups.

Of the above phosphorylated carboxylic acids, useful β-dithio phosphorylated propanoic acids have the structure of the following general formula (7).

Specific examples of such β-dithiophosphorylated propanoic acid that may be mentioned include 3-(di-isobutoxy-thiophosphorylsulfanyl)-2-methyl-propanoic acid.

There is no particular restriction regarding the content of phosphorus-containing carboxylic acid compounds in the present lubricating oil composition, but this content is preferably 0.001 to 1 weight %, more preferably 0.002 to 0.5 weight % with respect to 100 weight % of base oil.

If the content of phosphorus-containing carboxylic acid compounds is less than the above lower limit, sufficient lubricating performance tends not to be obtained. On the other hand, if more than the above upper limit is added, a lubrication improving effect matching the added content tends not to be attained, and, furthermore, there is a risk of impairment of heat/oxidation stability and/or hydrolysis stability, so this is therefore undesirable.

It should be noted that, in the phosphorylated carboxylic acids represented by the above general formula (6), the content of compounds in which R7 is a hydrogen atom is 0.001 to 0.1 weight %, preferably more 0.002 to 0.08 weight %, more preferably 0.003 to 0.07 weight %, even more preferably 0.004 to 0.06 weight %, and yet more preferably 0.005 to 0.05 weight %.

Polyhydric alcohol fatty acid esters may be blended with the lubricating oil composition according to the present invention with the object of improving oiliness. For example partial or complete esters of saturated or unsaturated fatty acids of carbon number 1 to 24 of polyhydric alcohols such as glycerol, sorbitol, alkylene glycols, neopentyl glycol, trimethylol propane, pentaerythritol or xylitol may be employed. As glycerol esters, there may be mentioned by way of example glycerol monolaurate, glycerol monostearate, glycerol monopalmitate, glycerol mono-oleate, glycerol dilaurate, glycerol distearate, glycerol dipalmitate or glycerol dioleate.

As sorbitol esters, there may be mentioned by way of example sorbitol monolaurate, sorbitol monopalmitate, sorbitol monostearate, sorbitol monooleate, sorbitol dilaurate, sorbitol dipalmitate, sorbitol distearate, sorbitol dioleate, sorbitol tristearate, sorbitol trilaurate, sorbitol trioleate, or sorbitol tetraoleate.

As alkylene glycol esters, there may be mentioned by way of example ethylene glycol monolaurate, ethylene glycol monostearate, ethylene glycol mono-oleate, ethylene glycol dilaurate, ethylene glycol distearate, ethylene glycol dioleate, propylene glycol monolaurate, propylene glycol monostearate, propylene glycol mono-oleate, propylene glycol dilaurate, propylene glycol distearate or propylene glycol dioleate.

As neopentyl glycol esters, there may be mentioned by way of example neopentyl glycol monolaurate, neopentyl glycol monostearate, neopentyl glycol mono-oleate, neopentyl glycol dilaurate, neopentyl glycol distearate, or neopentyl glycol dioleate.

As trimethylol propane esters, there may be mentioned by way of example trimethylol propane monolaurate, trimethylol propane monostearate, trimethylol propane mono-oleate, trimethylol propane dilaurate, trimethylol propane distearate, trimethylol propane dioleate, or pentaerythritol monolaurate.

As pentaerythritol esters, there may be mentioned by way of example pentaerythritol monostearate, pentaerythritol mono-oleate, pentaerythritol dilaurate, pentaerythritol distearate, pentaerythritol dioleate, or pentaerythritol mono-oleate. As fatty acid esters of such polyhydric alcohols, preferably partial esters of polyhydric alcohols and unsaturated fatty acids are employed.

In order to improve low temperature fluidity or viscosity performance in respect of the lubricating oil composition according to the present invention, pour-point depressants or viscosity index improving agents may be added. As viscosity index improving agents, there may be mentioned by way of example non-dispersive viscosity index improving agents such as polymethacrylate or ethylene-propylene copolymer, styrene-diene copolymer, or olefin polymers such as poly-isobutylene, or polystyrene, or dispersive viscosity index improving agents obtained by copolymerization of a nitrogen-containing monomer with these. These may be employed in a range of 0.05 to 20 weight % with respect to 100 weight % of base oil. As pour-point depressants, there may be mentioned by way of example polymethacrylate-based polymers. These may be employed in a range of 0.01 to 5 weight % with respect to 100 weight % of base oil.

In order to confer anti-foaming properties on the lubricating oil composition according to present invention, an anti-foaming agent may be added. As anti-foaming agents suitable in the present invention, there may be mentioned by way of example organosilicates such as dimethyl polysiloxane, diethyl silicate, or fluorosilicones, or non-silicone anti-foaming agents such as polyalkylacrylates. These may be employed either alone or in a combination of two or more thereof, in a range of 0.0001 to 0.1 weight % with respect to 100 weight % of base oil.

As anti-emulsifiers suitable in the present invention, there may be mentioned by way of example known anti-emulsifiers that are employed as ordinary lubricating oil additives. These may be employed in a range of 0.005 to 0.5 weight % with respect to 100 weight % of base oil.

PRACTICAL EXAMPLES

Various practical examples of the present invention and comparative examples are specifically described below: however, the present invention is not restricted solely to these practical examples

In preparation of the practical examples and comparative examples, materials of the following compositions were prepared.

1. Base Oil

(1-1) Base oil 1: paraffin-based mineral oil obtained by application in suitable combination of purifying means such as hydrocracking and dewaxing to a lubricating oil fraction obtained by distillation of crude oil at normal pressure, classified in Group II (Gp II) in the API (American Petroleum Institute) base oil classification. (Properties:—kinetic viscosity at 100° C.: 1.35 mm²/s; kinetic viscosity at 40° C.: 31.4 mm²/s; viscosity index: 103; 15° C. density: 0.864; sulphur content (value calculated as elementary sulphur): less than 10 ppm; nitrogen content (value calculated as elementary nitrogen): less than 1 ppm; aniline point: 110° C.; ring analysis paraffin fraction using the ASTM D3238 method: 62%; ring analysis naphthene fraction: 38%; ring analysis aromatics fraction: less than 1%; initial boiling point temperature by gas chromatographic distillation using the ASTM D5480 method: 312° C.).

(1-2) Base oil 2: paraffin-based mineral oil obtained by application in suitable combination of purifying means such as hydrocracking and dewaxing to a lubricating oil fraction obtained by distillation of crude oil at normal pressure, classified in Group III (Gp III) in the API (American Petroleum Institute) base oil classification. (Properties:—kinetic viscosity at 100° C.: 6.57 mm²/s; kinetic viscosity at 40° C.: 37.5 mm²/s; viscosity index: 130; 15° C. density: 0.823; sulphur content (value calculated as elementary sulphur): less than 10 ppm; nitrogen content (value calculated as elementary nitrogen): less than 1 ppm; aniline point: 130° C.; ring analysis paraffin fraction using the ASTM D3238 method: 78%; ring analysis naphthene fraction: 22%; ring analysis aromatics fraction: less than 1%; polycyclic aromatics fraction using the IP 346 method: 0.2%)

(1-3) Base oil 3: this is a GTL base oil synthesised using the Fischer-Tropsch method: classified as Group III in the API (American Petroleum Institute) base oil classification. (Properties:—kinetic viscosity at 100° C.: 5.10 mm²/s; kinetic viscosity at 40° C.: 23.5 mm²/s; viscosity index: 153; 15° C. density: 0.821; sulphur content (value calculated as elementary sulphur): less than 10 ppm; nitrogen content (value calculated as elementary nitrogen): less than 1 ppm; ring analysis aromatics fraction using the ASTM D3238 method: less than 1%.

(1-4) Base oil 4: poly-α-olefins (PAO) of synthetic oil, general name PAO6 classified as Group IV in the API (American Petroleum Institute) base oil classification. (Properties:—kinetic viscosity at 100° C.: 5.89 mm²/s; kinetic viscosity at 40° C.: 31.2 mm²/s; viscosity index: 135; 15° C. density: 0.827; sulphur content (value calculated as elementary sulphur): less than 10 ppm; nitrogen content (value calculated as elementary nitrogen): less than 1 ppm; aniline point: 128° C.; ring analysis aromatics fraction using the ASTM D3238 method: less than 1%; initial boiling point temperature by gas chromatographic distillation using the ASTM D5480 method: 403° C.).

(1-5) Base oil 5: paraffin-based mineral oil obtained by application in suitable combination of purifying means such as dewaxing to a lubricating oil fraction obtained by distillation of crude oil at normal pressure, classified in Group I (Gp I) in the API (American Petroleum Institute) base oil classification. (Properties:—kinetic viscosity at 100° C.: 4.60 mm²/s; kinetic viscosity at 40° C.: 24.6 mm²/s; viscosity index: 101; 15° C. density: 0.866; sulphur content (value calculated as elementary sulphur): 460 ppm; nitrogen content (value calculated as elementary nitrogen): 20 ppm; ring analysis paraffin fraction using the ASTM D3238 method: 66%; ring analysis naphthene fraction: 31%; ring analysis aromatics fraction: 3%; aniline point: 99° C.; polycyclic aromatics fraction using the IP 346 method: 0.8%; initial boiling point temperature by gas chromatographic distillation using the ASTM D5480 method: 331° C.).

2. Additives

(2-1) Additive A1: aspartic acid derivative: K-CORR 100 manufactured by King Inc (acid value in accordance with the method of JIS K2501: 100 mg KOH/g)

(2-2) Additive A2: aspartic acid derivative: COLACOR93 manufactured by Colonial Chemicals Inc (acid value in accordance with the method of JIS K2501: 75 mg KOH/g);

(2-3) Additive A3: aspartic acid derivative: MONACOR39 manufactured by Unichema Inc (acid value in accordance with the method of JIS K2501: 60 mg KOH/g)

(2-4) Additive B1: coconut amine (chief constituent dodecylamine): primary alkyl primary amine compound (base value in accordance with the method of JIS K2501: 390 mg KOH/g)

(2-5) Additive B2: oleylamine: primary alkyl primary amine compound (base value in accordance with the method of JIS K2501: 215 mg KOH/g)

(2-6) Additive B3: tallow amine (chief constituent: oleylamine, stearylamine, palmitylamine): primary alkyl primary amine compounds (base value in accordance with the method of JIS K2501: 215 mg KOH/g)

(2-7) Additive B4: primary amine of C18 tertiary alkyl group: tertiary alkyl primary amine compound (base value in accordance with the method of JIS K2501: 155 mg KOH/g)

(2-8) Additive B5: coconut secondary amine (chief constituent didodecylamine): primary alkyl secondary amine compound (base value in accordance with the method of JIS K2501: 160 mg KOH/g)

(2-9) Additive B6: coconut diamine (chief constituent N-dodecyl-1,3-propylene diamine) (base value in accordance with the method of JIS K2501: 440 mg KOH/g)

(2-10) Additive B7: tallow diamine (chief constituents N-oleyl-1,3-propylene diamine, N-stearylamine-1,3-propylene diamine, N-palmityl-1,3-propylene diamine) (base value in accordance with the method of JIS K2501: 330 mg KOH/g)

(2-11) Additive B8: N-alkyl diethanolamines (chief constituent N-dodecyl dimethylamine): tertiary amine compound (base value in accordance with the method of JIS K2501: 160 mg KOH/g)

(2-12) Additive B9: N-alkyl diethanolamines (chief constituent N-oleyl diethanolamine): tertiary amine compound (base value in accordance with the method of JIS K2501: 160 mg KOH/g)

(2-13) Other additives: the compounds indicated below may also be added:—diphenylamine, phenyl naphthylamine, benzene propanoic acid 3,5-bis(1,1-dimethyl-ethyl)-4-hydroxy-C7 to C9 side-chain alkyl esters, N,N-bis(2-ethyl hexyl)-(4 or 5)-methyl-1H-benzotriazole-1-methylamine, triallyl phosphate, 3-(di-isobutoxy-thiophosphoryl sulfanyl)-2-methyl-propionic acid, pentaerythritol esters, polymethacrylate-based pour-point depressants, dimethyl polysiloxane-based anti-foaming agents, and polyoxyethylene and/polyoxypropylene glycol-based anti-emulsifiers.

Examples 1 to 19, Comparative Examples 1 to 5

The lubricating oil compositions of Examples 1 to 19 and Comparative Examples 1 to 5 were prepared with the compositions indicated in Table 1 to Table 5, using materials of the above composition.

Tests

In order to evaluate the performance of the lubricating oil compositions of Examples 1 to 19 and Comparative Examples 1 to 5, the following anti-rust performance test was conducted and the coefficient of friction was measured using a pendulum test.

Anti-Rust Performance Test

In accordance with JIS K2510, 300 ml of sample oil were taken in a container arranged in a constant temperature bath, stirring conducted by rotating at 1000 rpm, and an iron test piece was inserted in the sample oil when a temperature of 60° C. had been reached: 30 ml of artificial seawater was then added, and stirring continued for 24 hours, maintaining the temperature at 60° C. The test piece was then extracted, and a visual evaluation as to whether or not rusting of the test piece had occurred was conducted: if no rust was generated, the sample was deemed to have passed the test.

Pendulum Test/Coefficient of Friction

The coefficient of friction was measured at 25° C. by a Masuda type pendulum oil properties testing machine, manufactured by Shinko Zoki Inc. In this test, the sample oil is supplied to the friction location of the pendulum fulcrum, the pendulum is oscillated, and the coefficient of friction is found from the damping of the oscillations.

Evaluation in the test was conducted in accordance with the following criteria.

-   -   Coefficient of friction less than 0.135 . . . @ (excellent)     -   Coefficient of friction in the range 0.135 to less than 0.150 .         . . O (satisfactory)     -   Coefficient of friction 0.150 or more . . . X (unsatisfactory)

Test Results

The results of the tests are shown in Table 1 to Table 5.

Discussion

As shown in Examples 1 to 3 of Table 1, by use of an aspartic acid derivative and aliphatic amine with the base oil 1, anti-rust properties are provided that pass the anti-rust properties test, and the coefficient of friction can be lowered.

Also, it can be seen that an aspartic acid derivative can be employed alone as shown in Examples 1 to 3, or a mixture thereof can be employed, as shown in Example 4. Furthermore, as shown in Example 5, good results are obtained even when a mixture of both an aspartic acid derivative and aliphatic amine is employed.

Also, as shown in Examples 6 to 9 of Table 2, excellent anti-rust properties and low friction are obtained also with a lubricating oil composition employing as base oil any of the highly purified base oil 2 to base oil 5. And, as shown in Example 10, it can be seen that the excellent anti-rust properties and low friction effect produced by the combination of aspartic acid derivative and aliphatic amine as described above is also effective when other additives are used together therewith.

In Examples 11 to 18 of Table 3 and Table 4, it can be seen that excellent anti-rust properties and excellent low friction properties are obtained by a combination of an aspartic acid derivative (additive A1) and various types of aliphatic amine compounds (additives B2 to B9). Also, good results are obtained when the aliphatic amine compounds of Example 19 are mixed therewith. In particular, by the use of the aliphatic amine compounds of additives B6 to B9 shown in Examples 15 to 19, mixed with additives B1 to B4, very considerable reduction in the coefficient of friction can be achieved and excellent energy-saving properties can thereby be conferred on the lubricating oil composition.

In contrast, it is clear from the test results shown in Table 5 that, in the case where the base oil 1 of Comparative Example 1 was employed alone, its anti-rust performance did not pass the test and the frictional coefficient was also unsatisfactory. Also, although, in the case of the lubricating oil compositions wherein an aspartic acid derivative (additives A1 to A3) was added to the base oils of Comparative Examples 2 to 4, the anti-rust properties passed the test, these compositions were unsatisfactory due to a high coefficient of friction. It can further be seen that, even in the case of the lubricating oil composition wherein an aliphatic amine (Additive B1) was added to the base oil of Comparative Example 5, the anti-rust performance did not pass the test and the frictional coefficient was also high, making the lubricating oil composition unsatisfactory.

TABLE 1 Example 1 Example 2 Example 3 Example 4 Example 5 Composition Base oil 1: 99.7 99.7 99.7 99.7 99.7 Gp II Additive A1: 0.1 0.05 0.05 Aspartic acid derivative K-CORR100 Additive A2: 0.1 0.05 Aspartic acid derivative COLACOR93 Additive A3: 0.1 0.05 Aspartic acid derivative MONACOR39 Additive B1: 0.2 0.2 0.2 0.2 0.1 Coconut amine Additive B6: 0.1 Coconut diamine Test results Antirust test Pass Pass Pass Pass Pass Pendulum test @ @ ◯ @ @ Coefficient of 0.125 0.120 0.145 0.130 0.134 friction

TABLE 2 Example Example 6 Example 7 Example 8 Example 9 10 Composition Base oil 2: Gp III 99.7 Base oil 3: GTL 99.7 99.2 Base oil 4: PAO 99.7 Base oil 5: Gp I 99.7 Additive A1: 0.1 0.1 0.1 0.1 0.1 Aspartic acid derivative K-CORR100 Additive B1: 0.2 0.2 0.2 0.2 0.2 Coconut amine Other additives 0.5 Test results Antirust test Pass Pass Pass Pass Pass Pendulum test @ @ @ @ @ Coefficient of 0.122 0.130 0.134 0.130 0.123 friction

TABLE 3 Example 11 Example 12 Example 13 Example 14 Composition Base oil 1: Gp 99.7 99.7 99.7 99.7 II Additive A1: 0.1 0.1 0.1 0.1 Aspartic acid derivative K-CORR100 Additive B2: 0.2 Oleylamine Additive B3: 0.2 Tallow amine Additive B4: 0.2 Tertiary alkyl primary amine Additive B5: 0.2 Coconut secondary amine Test results Antirust test Pass Pass Pass Pass Pendulum test @ @ ◯ ◯ Coefficient of 0.129 0.126 0.139 0.139 friction

TABLE 4 Example Example Example Example Example 15 16 17 18 19 Composition Base oil 1: Gp 99.7 99.7 99.7 99.7 99.7 II Additive A1: 0.1 0.1 0.1 0.1 0.1 Aspartic acid derivative K-CORR100 Additive B1: 0.1 Coconut amine Additive B4: 0.1 Tertiary alkyl primary amine Additive B6: 0.2 Coconut diamine Additive B7: 0.2 Tallow diamine Additive B8: 0.2 N-alkyl- diethanolamine (1) Additive B9: 0.2 N-alkyl- diethanolamine (2) Test results Antirust test Pass Pass Pass Pass Pass Pendulum test @ @ @ @ @ Coefficient of 0.113 0.114 0.119 0.113 0.116 friction

TABLE 5 Comparative Comparative Comparative Comparative Comparative Example 1 Example 2 Example 3 Example 4 Example 5 Composition Base oil 1: 100 99.9 99.9 99.9 99.8 Gp II Additive A1: 0.1 Aspartic acid derivative K-CORR100 Additive A2: 0.1 Aspartic acid derivative COLACOR93 Additive A3: 0.1 Aspartic acid derivative MONACOR39 Additive B1: 0.2 Coconut amine Test results Antirust test Fail Pass Pass Pass Fail Pendulum X X X X X test 0.307 0.167 0.155 0.181 0.193 Coefficient of friction 

1-13. (canceled)
 14. A lubricating oil composition comprising a base oil, an aspartic acid derivative, and an aliphatic amine compound.
 15. The lubricating oil composition of claim 14, wherein the aspartic acid derivative has an acid value of that is at least 10 and no greater than 200 mg KOH/g.
 16. The lubricating oil composition of claim 14, wherein the aspartic acid derivative is at an amount that is at least about 0.01 and no greater than about 5 weight % of the lubricating oil composition and the aliphatic amine compound is at an amount that is at least about 0.005 and no greater than about 5 weight % of the lubricating oil composition
 17. The lubricating oil composition of claim 14, wherein the aliphatic amine compound comprises a primary amine represented by the formula H₂N—X₅ where X₅ is an alkyl group or alkenyl group of carbon number 1 to
 30. 18. The lubricating oil composition of claim 14, wherein the aliphatic amine compound further comprises a secondary amine represented by the formula X₆—NH—X₇ where X₆ and X₇ are an alkyl group or alkenyl group of carbon number 1 to
 30. 19. The lubricating oil composition of claim 14, wherein the aliphatic amine compound comprises a diamine represented by the formula X₈—NH—X₉—NH₂ where X₅ is an alkyl group or alkenyl group of carbon number 1 to 30 and X₉ is an alkylene group of carbon number 1 to
 12. 20. The lubricating oil composition of claim 14 wherein the aliphatic amine compound comprises a tertiary amine represented by the formula X₁₀—NH—(X₁₁)₂ where X₁₀ is an alkyl group or alkenyl group of carbon number 1 to 30 and X₁₁ is an alkyl group, alkenyl group, or hydroxyalkyl group of carbon number 1 to
 20. 21. The lubricating oil composition of claim 14 further comprising an aromatic amine compound, a phenol compound, or both.
 22. The lubricating oil composition of claim 14, wherein said base oil is a synthetic oil.
 23. The lubricating oil composition of claim 22, wherein said synthetic oil is a poly-α-olefin or GTL.
 24. A lubricating oil composition comprising a base oil, an aspartic acid derivative at an amount that is at least about 0.01 and no greater than about 5 weight % of the lubricating oil composition, and an aliphatic amine compound at an amount that is at least about 0.005 and no greater than about 5 weight % of the lubricating oil composition, wherein the aspartic acid derivative has an acid value that is at least 10 and no greater than 200 mg KOH/g, and wherein the aliphatic amine compound comprises: a primary amine represented by the formula H₂N—X₈ where X₅ is an alkyl group or alkenyl group of carbon number 1 to 30; a secondary amine represented by the formula X₆—NH—X₇ where X₆ and X₇ are an alkyl group or alkenyl group of carbon number 1 to 30; a diamine represented by the formula X₈—NH—X₉—NH₂ where X₈ is an alkyl group or alkenyl group of carbon number 1 to 30 and X₉ is an alkylene group of carbon number 1 to 12; and a tertiary amine represented by the formula X₁₀—NH—(X₁₁)₂ where X₁₀ is an alkyl group or alkenyl group of carbon number 1 to 30 and X₁₁ is an alkyl group, alkenyl group, or hydroxyalkyl group of carbon number 1 to
 20. 25. A method of lubricating an apparatus, the method comprising lubricating the apparatus with a lubricating oil composition that comprises a base oil, an aspartic acid derivative, and an aliphatic amine compound.
 26. The method of claim 25, wherein the aspartic acid derivative has an acid value of that is at least 10 and no greater than 200 mg KOH/g.
 27. The method of claim 25, wherein the aspartic acid derivative is at an amount that is at least about 0.01 and no greater than about 5 weight % of the lubricating oil composition and the aliphatic amine compound is at an amount that is at least about 0.005 and no greater than about 5 weight % of the lubricating oil composition
 28. The method of claim 25, wherein the aliphatic amine compound comprises a primary amine represented by the formula H₂N—X₅ where X₅ is an alkyl group or alkenyl group of carbon number 1 to
 30. 29. The method of claim 25, wherein the aliphatic amine compound further comprises a secondary amine represented by the formula X₆—NH—X₇ where X₆ and X₇ are an alkyl group or alkenyl group of carbon number 1 to
 30. 30. The method of claim 25, wherein the aliphatic amine compound comprises a diamine represented by the formula X₈—NH—X₉—NH₂ where X₈ is an alkyl group or alkenyl group of carbon number 1 to 30 and X₉ is an alkylene group of carbon number 1 to
 12. 31. The method of claim 25 wherein the aliphatic amine compound comprises a tertiary amine represented by the formula X₁₀—NH—(X₁₁)₂ where X₁₀ is an alkyl group or alkenyl group of carbon number 1 to 30 and X₁₁ is an alkyl group, alkenyl group, or hydroxyalkyl group of carbon number 1 to
 20. 32. The method of claim 25, wherein the lubricating oil composition further comprises an aromatic amine compound, a phenol compound, or both.
 33. The method of claim 25, wherein said base oil is a synthetic oil.
 34. The method of claim 33, wherein said synthetic oil is a poly-α-olefin or GTL. 